This invention relates to a velocity monitoring system for use in connection with an apparatus for positioning a first component relative to a second component. The monitoring system of this invention is particularly useful in connection with positioning apparatus of the type which includes drive means for moving the first component, means for controlling the drive means to move the first component at a desired velocity, and means for measuring the actual position of the first component with respect to the second component and for generating position values representative thereof.
Positioning devices of the general type described above are known to the art. In the German publication ELEKTRONIK (1980, No. 18, pp. 47-54) there is described a positioning system in which electromechanical components are used to position an object to preselected spatial positions in response to presettable variable inputs.
In this positioning system there is provided a speed regulating circuit which operates to control a drive motor in such a way that the velocity of the component being moved is increased initially, and this velocity is reduced before the component reaches the desired position. In this way, the component does not overrun the desired position.
The disclosed positioning device regulates the velocity of the component being moved in response to the output of a tachogenerator coupled to the motor, which provides direct measured values of the component speed. The regulated speed can, therefore, be erroneous if the tachogenerator fails for any reason. In the event of an error in the speed regulation of the motor, the safety of the operator can be endangered. Furthermore, the positioning system itself, as well as any workpiece being formed, can be severely damaged if the first component is caused to move at an erroneous speed.